The present invention relates to chemically treated glass fibers for reinforcing polymeric matrices in producing reinforced polymers or plastics. More particularly, the present invention is directed to chopped, chemically treated glass fibers and strands for use in reinforcing polyolefin polymeric matrices to produce glass fiber reinforced polymers or plastics.
Glass fibers as continuous fibers, strands and rovings and chopped fibers and strands have been used to reinforce various polymeric matrices and have been useful in reinforcing polyolefins. The fibers usually are treated during their formation with a chemical treating composition usually referred to as a sizing composition to protect the fibers in subsequent processing and to assist the fibers in adhering with the polymeric matrix.
Polymers of the alpha-olefin, monomer type such as polypropylene that are to be reinforced with glass fibers exist in several stereo isometric forms. The term "polypropylene polymers" is inclusive of all polymers derived from propylene whether essentially amorphous or essentially crystalline, and including copolymers such as block copolymers of propylene with one or more other monomers. In addition, polyolefins that are to be reinforced with glass fibers have been developed that are propylene acid compounds and that are blends of isotactic and amorphous polypropylenes. Illustrative examples of the polypropylene acid compounds are acid-modified propylene polymers such as those taught in U.S. Pat. Nos. 3,416,990 (Robinson); and 3,437,550 (Paul) and an article published by the Society of Automotive Engineers entitled "Properties of Reinforced Propylene/Acid Compounds by R. A. Van Brederode, R. A. Steinkamp, K. W. Bartz, K. L. Trachte, and D. G. Steinmark, number 740292, February-March, 1974. Illustrative examples of blends of isotactic and amorphous polypropylenes are presented in U.S. Pat. Nos. 3,073,790 and 3,483,276.
Glass fibers that have been manufactured to reinforce polymers like polyolefins have been produced with chemical treating compositions on the surfaces of the glass fibers such as those taught in U.S. Pat. Nos. 3,655,353, 3,849,148, 3,882,068, 3,814,715 (Nalley et al.). To prepare the glass fibers for reinforcing polyolefins, the aqueous chemical treating composition usually has a resinous binder which is usually an aqueous polyolefin emulsion. This emulsion can be a propylene emulsion, a polypropylene polyethylene emulsion or carboxylated polypropylene emulsion or carboxylated polypropylene-polyethylene emulsion. Also in my recent U.S. Pat. No. 4,240,944, I taught sized glass fiber strands having an aqueous chemical treating composition of an aqueous emulsion of an isotactic carboxylated polypropylene and an amorphous carboxylated polypropylene, a coupling agent, a film former and a lubricant. The aqueous emulsion of the blended polypropylenes was produced as described in U.S. Pat. No. 4,283,322 by blending the isotactic carboxylated polypropylene and amorphous carboxylated polypropylene in specific ratios with a base in an amount to produce an equivalent alkalinity to that produced by potassium hydroxide sufficient to provide a residual content of hydroxides ranging from about 16 to about 25 milligrams of hydroxide per gram of emulsion along with a surfactant and water wherein the pH of the emulsion is in the range of 8 to 9.5. The sized glass fiber strands of U.S. Pat. No. 4,283,322 performed well in reinforcing the carboxylated polypropylenes.
The basic problem with reinforcing a polyolefin matrix with glass fibers is that the polyolefin without carboxylation has no chemical moieties which can interact with any chemicals present in an aqueous chemical treating composition on the glass fibers short of degrading the polypropylene to an extent through free radical polymerization with materials in the aqueous chemical treating composition. The carboxylated polyolefin provide chemical moieties such as the carboxylate groups which can interact with chemical moieties in the aqueous chemical treating composition or its residue on the glass fibers. In reinforcing polyolefin polymers with glass fibers, the industry is always striving for stronger bonds between the glass fibers and the polyolefin matrix to provide for stronger more durable glass fiber reinforced polyolefins. This is especially true when the matrix polyolefin is an uncoupled polyolefin not having any carboxylation but rather unmodified polyolefin homopolymer. The art in striving for better reinforcement of polyolefins desires improvements in such properties as strength properties of the reinforced polyolefin and less thermal deterioration of these properties. Also, it would be beneficial in producing chemically treated glass fibers for reinforcing polyolefins to produce the chopped glass fiber strands directly during the formation of the glass fibers rather than forming the glass fibers as continuous strands in a multilayered package and subsequently wet or dry chopping the glass fibers.
It is an object of the present invention to provide chemically treated glass fibers for reinforcing polyolefins to result in more thermally and oxidatively stable glass fiber reinforced polyolefins.
It is an additional object of the present invention to provide chemically treated glass fibers for reinforcing either chemically modified or chemically unmodified polyolefin to result in glass fiber reinforced polyolefins having good mechanical properties.